The invention concerns an industrial robot endowed with an articulated manipulator having a main rotating arm coupled mechanically to a forearm fixed to the gripping component and governed by a programmable controller that controls and monitors the robot's operating cycle.
The use of robots in the plastics processing industry to carry out various post-moulding and unloading operations is not new. The robots used are of the general purpose type with at least six degrees of freedom and are high performance robots. However, their kinematic structure and control system are complicated and the corresponding high cost weighs heavily in the amortization of capital expenditure.
The traditional manipulator systems used in the plastics processing industry have the following disadvantages:
automation is not total and consequently a work station must be maintained on the machine;
they are poorly adapted to short series (adjustment time);
additional machines must be adjoined for conditioning operations; and
special adaptations must be provided in the case of particular stripping trajectories.
The industrial robot according to this invention is a middle term between manipulators and the general purpose robots with six degrees of freedom. It comprises a reliable and inexpensive system, with three axes, permitting all stripping and post-moulding functions.
The kinematic system of the manipulator according to the invention comprises:
a first means of vertical transfer provided between the gripping component and the free end of the forearm;
a swivel link between the main arm and the forearm composed of a vertical free-turning spindle onto which said arms are mounted by means of ball-bearings;
another vertical spindle supporting the main arm lying parallel to the free-turning spindle of the coupling in such a way that the two arms swivel round their respective spindles in a fixed horizontal plane to form a kinematic system functioning in cylindrical coordinates;
a first servo-motor driving the main arm;
a second servo-motor driving the forearm;
an auxiliary system to transmit the movement of the arms composed of a pair of gear-wheels fixed permanently at opposite ends of the loose spindle of the coupling, each co-operating with endless drive belts lying in the direction of the forearm and the main arm; and
programming means co-operating with the servo-motors in order to co-ordinate the two servo-controlled rotating motions of the arms, so that the gripping component is driven through a linear trajectory at the beginning of the robot's operating cycle.
One of the particular features of the invention is that the belt corresponding to the forearm is wound between one of the gear-wheels of the auxiliary transmission system and a gear-wheel fixed to the first means of vertical transfer, and the belt corresponding to the main arm co-operates with the opposite gear-wheel on the spindle and another gear-wheel mounted coaxially with the supporting spindle, this last gear-wheel being either fast or adjustable in rotation in relation to the relative position of the rotating spindle of the main arm. The main arm is longer than the forearm and the angular travel B of the spindle supporting the main arm is greater than angular travel C of the forearm about the spindle of the coupling, the kinematic system being designed so that the circular trajectory T.sub.1 of the swivel link during the angular travel B of the arm lies within the annular sector swept by the arms of the kinematic system, this sector being delimited by two concentric circular arcs T.sub.2, T.sub.3 centered on the spindle and constituting the trajectories of the means of vertical transfer for the extreme values of the angular travel C of the forearm.
Another feature of the invention is that the first means of vertical transfer comprises a jack and rod driving a piston moving in either direction of linear travel F between two preset upper and lower limiting positions, said jack rod being off-set radially in relation to the axis of the piston, so as to constitute an anti-rotation guide system. A releasable coupling system with a memory device is provided for the tool-holder in order to permit, on the one hand, the momentary disconnection of the tool from the tool-holder in the event of abnormal loads, and, on the other hand, the return of the tool to its start-of-work position.
Another feature of the invention is that the control system of each servo-motor includes an on-off position detector DP placed at a predetermined location on the angular travel B or C of the corresponding arm, and a transitory readjustment system of the said arm to a starting position when the first zero index signal (PTO) is detected following the change of status of the position detector DP.